Virtual channel table for a broadcast protocol and method of broadcasting and receiving broadcast signals using the same

ABSTRACT

A virtual channel table for broadcasting protocol and a method for broadcasting by using the virtual channel table includes identification information identifying and permitting discrimination of active and inactive channels contained in the virtual channel table. At a receiver, the virtual channel table transmitted from the transmitting side is parsed, thereby determining whether the current received channel is an active or inactive channel.

This application claims the benefit of Korean Patent Application No.1999-43508, filed on Oct. 8, 1999, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a virtual channel table for a broadcastprotocol and a method of broadcasting using the same.

2. Discussion of the Related Art

Generally, a program and system information protocol (hereinafter,referred to as PSIP) of an Advanced Television Systems Committee(hereinafter, referred to as ATSC) standard for digital televisionbroadcasting contains a virtual channel table (VCT). “Program and SystemInformation Protocol For Terrestrial Broadcast and Cable,” ATSC DocumentA/65, 23 Dec. 1997, is hereby incorporated by reference for all purposesas if fully set forth herein.

The PSIP typically also contains an electronic program guide (EPG) andsystem information (SI). The PSIP is defined as the protocol of the ATSCstandard for terrestrial and cable digital television broadcasting whichparses encoded messages by using a moving picture experts group-2(MPEG-2; ISO/IEC 13818-1) system to thereby provide various kinds ofinformation on the broadcast programs (See ATSC document A/65, 23 Dec.1997).

In other words, the PSIP transmits and receives audio/video data withMPEG-2 video and AC-3 audio formats, and contains several tables fortransmitting information on the channel of each broadcasting station,and information on the programs on each channel. The PSIP has a primaryfunction of conducting the audio and video services of the broadcastcorresponding to a desired channel, and an additional function ofconducting the electronic program service for the broadcast programs.

The channel information for the channel selection and the packetidentification (PID) information for reception of the audio and videodata are contained in the virtual channel table (VCT), and theelectronic program service information on the broadcast programs on eachchannel is contained in an event information table (EIT). Also, the PSIPcontains a system time table (STT) for time information, a rating regiontable (RRT) for transmitting information on the region and organizationfor program rating, an extended text table (ETT) for providing anadditional explanation on the channel and broadcast program, and amaster guide table (MGT) for management of the version of each tablementioned above and the packet identification (PID). These tables aretransmitted in data units, which are called sections. Namely, all of thetables have one or more sections as a basic unit.

By way of example, the virtual channel table may be divided into 256sections. A single section may contain information on several virtualchannels, but information for a single virtual channel may not be spreadover on two or more sections.

FIG. 1 is a diagram illustrating the bit stream syntax of a generalvirtual channel table for terrestrial broadcast, which has beendescribed in the above-mentioned ATSC document A/65. The general virtualchannel table contains a transport stream identifier, a major channelnumber, a minor channel number, a short channel name, a carrierfrequency, a program number and the like, and contains additionalinformation in the descriptor(s) thereof.

Referring to FIG. 1, the virtual channel table has the table identifierfield of “0xC8,” and the value of the packet identification (PID) forthe virtual channel table is “0x1FFB.” The version number field“version_number” represents the version value of the virtual channeltable, the section number field “section_number ” represents acorresponding section number, the last section number field“last_section_number ” represents a last section number of the virtualchannel table, and the section number channel field“num_channels_in_section” represents the number of whole virtualchannels existing within the sections of the virtual channel table.

The short name field “short_name” within the statement in the “for_loop”represents the name of the virtual channel, and the major channel numberfield “major_channel_number” represents a major channel number among thevirtual channels defined in the statement mentioned above. Each virtualchannel number is connected to the major and minor channel numbers,respectively, and the major and minor channel numbers function as theuser reference number for the corresponding virtual channel. In otherwords, the virtual channel table carries the data for each virtualchannel through the statement of the “for_loop.”

The program number field “program_number” contains the information forconnecting the virtual channel where the MPEG-2 program associationtable (PAT) and program map table (PMT) are defined, which correspondsto the program numbers in the program association table and the programmap table. In this case, the program association table defines thecomponents of the program every program number, namely, indicates thepacket identification of the transport packet transmitting the programmap table. The program map table defines the list and the annexinformation thereof on the packet identification of the transport packettransmitting the program identification number and the bit stream of thevideo and audio signals constituting the program.

The source identifier field “source_id” represents the program sourceconnected to the corresponding virtual channel. In this case, the sourcemeans a specific source such as image, text, data or sound. The sourceidentifier field “source_id ” has a unique value in the transport streamtransmitting the virtual channel table. The descriptor length field“descriptors_length” indicates the whole length of the descriptors ofthe corresponding virtual channel, and the additional descriptor lengthfield “additional_descriptors_length” indicates the whole length of allof the additional descriptors of the virtual channel table.

FIG. 5 shows an exemplary list of descriptors for PSIP tables accordingto the ATSC standard.

FIG. 2 is a diagram illustrating an example of executing scheduledbroadcasting by using four virtual channels in a broadcasting station.

By way of example, it is assumed that the scheduled broadcast as shownin FIG. 2 is executed through the four virtual channels, 51-1, 51-2,51-3 and 51-8 in an arbitrary broadcast station and a virtual channeltable composed of a single section is transmitted.

If the current time is 20:15, the system time table transmits thecurrent time information. In this case, the channels 51-1 and 51-3 whichare broadcasting at the current time (20:15) are defined as the “activechannels.”

On the other hand, the channel 51-2 is not broadcasting at the currenttime and is going to be broadcast the next day, and the channel 51-8 isgoing to be broadcast next at 06:00. In this case, the channels 51-2 and51-8, which are not broadcasting at the current time (20:15) and aregoing to be broadcast in the future, are defined as the “inactivechannels.”

As a result, each channel may be an active or inactive channel, basedupon an arbitrary point in time.

Within the PSIP, the virtual channel table should contain the activechannels as required by the standard, and may also contain the inactivechannels as recommended by the standard, for conducting the electronicprogram guide service.

Therefore, at the current time (20:15) the virtual channel table maycontain information on all of the channels 51-1, 51-2, 51-3 and 51-8,and thus a digital television broadcast receiver or a digital cablebroadcast receiver receives the virtual channel table to thereby providethe channel selection information to TV viewers.

However, as shown in FIG. 1, according to the bit stream syntax of thevirtual channel table according to the ATSC document A/65, the digitaltelevision broadcast receiver or the digital cable broadcast receivercannot discriminate between the active channels (for example, thechannels 51-1 and 51-3) and the inactive channels (for example, thechannels 51-2 and 51-8), when parsing the virtual channel table.

As a consequence, the TV viewers see a black screen because of theinformation on the inactive channels transmitted from the broadcaststation for providing the electronic program guide. The black screenmeans the black background color is displayed on the screen when aninactive channel not broadcasting at a current time is selected. On theother hand, the character message “service not provided” is displayed onthe screen of the black background color by the on-screen displayfunction of the digital television broadcast receiver or the digitalcable broadcast receiver. By way of example, if the TV viewer selectsthe channel 51-2 with a channel up key while viewing the channel 51-1,the audio and video data are not displayed because the channel 51-2 isan inactive channel, such that the black background color is displayedon the screen.

The above-mentioned problem may give many inconvenience to the TVviewers at a point of time when digital television broadcast receiversor digital cable broadcast receivers become popular and a large numberof virtual channels are broadcast.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a virtual channeltable that substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a virtual channel tablefor a broadcast protocol, and a method of broadcasting by using the sametable, which are capable of identifying and permitting discriminationbetween active and inactive channels from the channels received by abroadcast receiver.

Another object of the invention is to provide a virtual channel tablefor a broadcast protocol, and a method of broadcasting by using the sametable, which are capable of rapidly displaying only the channels beingbroadcast at a current time.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

According to an aspect of the present invention, there is provided avirtual channel table for a broadcast protocol which comprisesidentification information capable of identifying and permittingdiscrimination between active and inactive channels in the bit streamsyntax thereof.

The identification information may be loaded on or included in at leastone reserved field in the virtual channel table. Preferably, theidentification information assigns at least one or more bits of areserved field as a flag, thereby indicating that a correspondingchannel is an inactive channel.

For example, the value of the program number field “program_number” inthe virtual channel table is set to “0,” thereby indicating that thecorresponding channel is the inactive channel.

The identification information sets the value of the number elementsfield “number elements” of the service position descriptor field“service_location_descriptor” in the virtual channel table to “0,”thereby indicating that the corresponding channel is an inactivechannel.

In a case where the corresponding channel is an inactive channel, thevirtual channel table does not contain the service location descriptorfield therein, for the purpose of indicating that the correspondingchannel is an inactive channel.

According to another aspect of the present invention, there is provideda method for broadcasting by using a virtual channel table for abroadcasting protocol, which comprises the steps of includingidentification information capable of identifying and permittingdiscrimination between active and inactive channels in the bit streamsyntax of the virtual channel table for a broadcasting protocol andtransmitting the virtual channel table, at a transmitting side; and, ata receiving side, determining whether the channel currently received isan active channel or an inactive channel with the identificationinformation defined in the virtual channel table by parsing the virtualchannel table transmitted.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a diagram illustrating the bit stream syntax of a generalvirtual channel table for terrestrial broadcast;

FIG. 2 is a diagram illustrating an example of executing schedulebroadcasting by using four virtual channels in a broadcast station;

FIG. 3 is a diagram illustrating the bit stream syntax of a virtualchannel table for terrestrial broadcast according to an embodiment ofthe present invention;

FIG. 4 is a diagram illustrating the bit stream syntax of a virtualchannel table for cable according to another embodiment of the presentinvention;

FIG. 5 is chart listing various descriptors available according to aprogram and system information protocol of an advanced televisionsystems committee standard digital television broadcast;

FIG. 6 is block diagram illustrating a digital television (DTV) receiveraccording to an embodiment of the present invention;

FIG. 7 is a diagram illustrating a preferred embodiment process ofhandling active and inactive channels for display in response to a userselection key;

FIG. 8 is a flowchart illustrating a preferred embodiment process ofproducing a display of a program or an electronic program guide (EPG)according to a channel or EPG selection key input by a user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which is illustrated in the accompanyingdrawings.

According to the present invention, a virtual channel table for abroadcast protocol comprises identification information capable ofidentifying and permitting discrimination between active and inactivechannels in the bit stream syntax thereof. A transmitting side, namely,a broadcast station transmits the virtual channel table having theidentification information to receivers. Each of receivers parses thevirtual channel table received, thereby determining whether the channelcurrently selected is an active channel or an inactive channel.

The identification information, which is capable of identifying andpermitting discrimination between an active channel and an inactivechannel under the standard of the PSIP, is contained in at least onefield of the virtual channel table of the above protocol, such that onlyactive channels being currently broadcast are displayed to TV viewers.

Hereinafter, preferred embodiments of a virtual channel table and amethod according to the present invention will be in detail describedwith reference to FIGS. 3 and 4.

In order for a digital television receiver and a digital cable broadcastreceiver to parse the virtual channel table and thus to determinewhether the channel selected currently is an active channel or aninactive channel, the bit stream syntax of the virtual channel table maybe corrected.

For example, the fact that channels 51-2 and 51-8 are not broadcast atthe current time 20:15, but are going to be broadcast in the future,should be recognized in a digital television receiver and a cablebroadcast receiver. In a preferred embodiment, the identificationinformation capable of identifying an inactive channel is contained inthe program number field “program_number,” the service locationdescriptor field “service_location_descriptor” and/or other reservedfields contained in the bit stream syntax of the virtual channel table.

FIG. 3 is a diagram illustrating the bit stream syntax of a virtualchannel table for terrestrial broadcast according to an embodiment ofthe present invention. To indicate that a corresponding channel is aninactive channel, the value of the program number field “program_number”is set to “0”. And, since there are no audio and video signals of thecurrent service location descriptor, the value of the number elementsfield “number_elements” of the service location descriptor“service_location_descriptor” is set to “0”. Also, or alternatively, toindicate that the corresponding channel is an inactive channel, theservice location descriptor “service_location_descriptor” (see FIG. 5)is not contained in the virtual channel table. In other words, thedigital television receiver and the cable broadcast receiver, theservice location descriptor field should be contained in the virtualchannel table only in a case where the corresponding channel is theactive channel. If the corresponding channel is an inactive channel,however, the service location descriptor field is not contained in thevirtual channel table.

In a preferred embodiment, in order to recognize the fact that thecorresponding channel is an inactive channel in a more apparent manner,1 bit of the reserved field of 6 bits for each channel is assigned todefine a flag indicative of an inactive channel. In the preferredembodiment, 1 bit in the reserved field between the hidden field“hidden” and the service type field “service_type” in the statement ofthe “for_loop” is assigned to define a flag indicative of an inactivechannel. For example, in a case where the flag indicative of theinactive channel is “1,” the corresponding channel is an active channel,and if the flag is “0,” the corresponding channel is an inactivechannel.

In the preferred embodiment, the above three cases may be added asrequirements in the document A/65. Any of all of the three cases may beadded in the document A/65.

As mentioned above, since the information on an inactive channel iscontained in the virtual channel table, the digital television receivercan determine whether the virtual channel currently received is anactive channel or an inactive channel by parsing only the virtualchannel table. For example, if the value of the program number field“program_number” in the virtual channel table is “0,” if the value ofthe information on the inactive channel defined by assigning apredetermined bit in the reserved field is “0,” or if the servicelocation descriptor field “service_location_descriptor” is not containedin the virtual channel table, the major channel number field“major_channel_number” and the minor channel number field“minor_channel_number” defined in the bit stream syntax of the virtualchannel table currently transmitted determine that the current virtualchannel is an inactive channel.

On the other hand, if an inactive channel has been determined under theabove process, the digital television receiver can skip the inactivechannel, without displaying it on the screen, upon channel conversion bymeans of a channel up key or a channel down key.

FIG. 4 is a diagram illustrating the bit stream syntax of a virtualchannel table for cable according to another embodiment. As shown, thevirtual channel table may be applied to cable broadcasting in the samemanner as above.

FIG. 6 shows a block diagram of a preferred embodiment of a digitaltelevision (DTV) receiver. A demodulator converts an RF signal to abaseband signal after channel error collection. Then, a transportdecoder separates several signals, such as audio, video, PSIP, etc. andoutputs the audio and video streams to audio and video decoders, and aPSIP data stream to a PSIP decoder. The PSIP Decoder decodes the PSIPdata stream for storing PSIP data in a PSIP database, and providesoutput to a user interface (UI) module for showing an active program oran EPG display.

Now, the PSIP decoder will be explained. A PSIP parser parses PSIPtables (VCT, EIT, STT, RRT, ETT, MGT) and the result is output to PSIPmain section. One can distinguish between active and inactive channelsby the parsing result. A section filter separates a necessary sectionfrom the PSIP data that was output by the transport decoder and outputsthe necessary data to the PSIP Parser.

A PSIP manager controls the PSIP database (DB). The PSIP Main sectioncontrols the transport decoder for receiving tables of PSIP data. ThePSIP Application Program Interface (API) provides an output to allow anexternal module to access PSIP DB. The Channel Manager and EPG Taskcomponents arc operated by user selection signal of the channel keyand/or EPG Key. If the user selects the channel key, the channel manageroutputs the channel changing signal to the demodulator and transportdecoder. In this case, a user can see an active channel. If the userselects the EPG key, the EPG Task component controls the PSIP Decoder tosupport an EPG display Mode. In this case, a user can see both activeand inactive channels, displayed in an EPG screen.

FIG. 7 shows channel surfing by using of the PSIP according to anembodiment of the present invention. At first, a channel is selected bya TV-user. And the transport decoder prepares to receive many signals,such as audio, video and PSIP transport packets. Next, the PSIP Decodersets a PID value of (0x1FFB) into the transport decoder to select theterrestrial virtual channel table (TVCT) of the PSIP, and gets the audioand video (A/V) PID values for the active virtual channels. (Inactivevirtual channels don't have A/V PID values, but have channel informationfor the EPG Service.) Then, the PSIP Decoder makes a channel map for thePSIP, sends it to the channel manager, to be used for tuning activechannels. Then, the channel manager sets A/V PIDs (Video PID 0x21, AudioPID 0x24) for virtual channel number (68-1) selected by the TV-user. Thetransport decoder receives the ATV transport packets, sends them to theA/V decoder(s), and finally the DTV channel will be serviced.

FIG. 8 shows a flowchart illustrating channel tuning and EPG Display.The user can see only the active channels displayed when tuningchannels, but when the user receives the EPG Service, he/she sees an EPGdisplay which includes all of the virtual channels, including theinactive channels.

As is apparent from the foregoing description, a virtual channel tablefor a broadcast protocol, and a method of broadcasting by using thevirtual channel table are capable of including the identificationinformation capable of identifying and permitting discrimination betweenactive and inactive channels in a transmitting side, and in a receivingside parsing the virtual channel table to thereby determine whether thechannel currently selected is the active channel or the inactivechannel. Therefore, inactive channels may be skipped, without beingdisplayed, upon the channel conversion by using a channel up key or achannel down key, such that the TV viewer can enjoy channel surfing in aconvenient manner, without viewing a black screen. In addition, thevirtual channel table may be transmitted, while containing the inactivechannels therein, thereby making it possible to provide a more abundantelectronic program service.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-30. (canceled)
 31. A method of processing a digital broadcastingsignal in a digital television receiver, comprising: demodulating adigital broadcasting signal including program and system informationprotocol (PSIP) data including a virtual channel table (VCT), andoutputting demodulated PSIP data, wherein the VCT includes a predefineddata field which is set to zero for an inactive channel, wherein theinactive channel is a channel that is not presently carrying a broadcastprogram; however, the same inactive channel is scheduled to carry abroadcast program at later time from a broadcasting station withoutlocal viewer interaction; and processing display of the correspondingvirtual channel, wherein when the virtual channel is currently inactive,the receiver is capable of skipping over the virtual channel while auser is surfing, wherein the VCT further includes a section_numberfield, wherein the VCT further includes a last_section_number field,wherein the VCT further includes a source_id field, and wherein the VCTfurther includes a description_length field.
 32. The method of claim 31,wherein the digital broadcasting signal is a digital terrestrialbroadcast signal.
 33. The method of claim 31, wherein the digitalbroadcasting signal is a digital cable broadcast signal.
 44. The methodof claim 31, wherein the predefined data field is included in astatement of a for_loop in a bit stream syntax of the VCT.